The present invention relates to water filters, and relates more particularly to such a water filter having sealing means that can effectively seal up the gap between the casing and the top cover of the water filter and prevent unfiltered water from enter the longitudinal center through hole of the filter element to mix with filtered clean water.
A variety of water filters have been disclosed, and have appeared on the market. FIGS. 1 and 2 show a water filter according to the prior art, which is generally comprised of a cylindrical casing having an inner thread around the top opening, a filter element received in the cylindrical casing, a top cover having an outer thread threaded into the inner thread of the cylindrical casing to hold down the filter element, and a packing ring sealed between the top cover and the cylindrical casing. The filter element has a longitudinal center through hole and two annular grooves on two opposite ends thereof. The cylindrical casing has a stub tube on the inside at the bottom inserted into the bottom end of the longitudinal center through hole of the filter element, and an annular flange fitted into the annular groove on the bottom end of the filter element. The top cover has a water outlet pipe fitted into the top end of the longitudinal center through hole of the filter element, and an annular flange fitted into the annular groove on the top end of the filter element. This structure of water filter is still not satisfactory in function because the packing ring will be twisted to deform, when the top cover is threaded into the inner thread of the cylindrical casing. Frequently deforming the packing ring will shorten the service life of the packing ring and affect its performance. Furthermore, because the annular flanges of the top cover and the cylindrical casing are of rigid structure, they deform the two opposite ends of the filter element when installed. When the filter element is installed in the cylindrical casing again after every washing process, the annular flanges of the top cover and the cylindrical casing must be accurately stopped at the dents on the two opposite ends of the filter element which was formed by the squeezing of the annular flanges, or water leakage will happen.
FIGS. 3 and 4 show another structure of water filter designed to eliminate the aforesaid drawbacks, in which the packing ring has a downward annular flange fitted into an annular groove around the inside wall of the cylindrical casing; two water sealing ring respectively mounted within an annular groove on the bottom wall of the top cover and an annular groove on the bottom wall of the cylindrical casing and sealed between the two opposite ends of the filter element and the bottom walls the top cover and cylindrical casing. The drawback of this structure of water filter is its complicated assembly process.